Conventionally, a power converter in which a PWM (Pulse Width Modulation) modulation method is used is well-known as a power converter used for driving a rotating electric machine having a three-phase coil. In such a power converter, harmonic noise resulting from on/off of switching elements may occur. Therefore, a technique for diffusing energy of harmonic noise in a broad frequency band by diffusing the carrier frequency to reduce the peak level of harmonic noise is publicly known.
As such a technique, Japanese Patent Laying-Open No. 2009-089550 (PTL 1), for example, discloses a power converter and a power conversion method that can further uniformize harmonic noise of carrier frequency. This power converter includes command value output means for outputting a command value, carrier wave power output means for outputting a carrier wave, carrier frequency changing means for changing the frequency of carrier wave, control signal generation means for comparing the command value and the carrier wave to generate a control signal based on the comparison result, and output means for outputting an output value based on the control signal. The carrier frequency changing means is characterized in that, as one value among a plurality of frequency values increases, the difference between the one value and a value adjacent to the one value in the case of arranging the plurality of values in an ascending order or descending order decreases.
According to the power converter disclosed in the above publication, harmonic noise of carrier frequency can be uniformized further.